Currently typical permanent magnet materials are alnico, hard ferrite and rare earth-cobalt magnets. The rare earth-cobalt magnets have been used in various fields due to their much excellent magnetic properties. However, it is now expected to encounter difficulty in stable supply of them in greater amounts and over an extended period of time, since the key components Sm and Co are both scarce and expensive.
For that reason, there has been an keen desire for permanent magnet materials excelling in magnetic properties and comprising compositional elements that are abundant and inexpensive, and will stably be supplied.
The present applicant (or company) has already proposed Fe-B-R base (wherein R is at least one of rare earth elements including Y) permanent magnets as the novel high-performance permanent magnets (Japanese Patent Kokai-Publication Nos. 59-46008, 59-64733, 59-89401 and 59-132104; EP publication of application Nos. 0101552, 0106948, 0126179, 0126802, 0124655 and 0125347). The permanent magnets disclosed therein are an excellent permanent magnet in which abundant rare earth elements, mainly Nd and/or Pr, are used as R, and R, B and Fe constitutes the main components, and which shows a practical energy product of at least 4 MGOe or 10 MGOe, as well as an extremely high energy product of 20, 25, 30, 35 MGOe or higher.
With the recent trend to high performance and diminishing sizes of magnetic circuits, increasing attention has been paid to Fe-B-R base permanent magnet materials. In the production of permanent magnet materials for that purpose, formed (compacted) and sintered magnet bodies have to be cut on the entire surface or the required surface portion for removing surface irregularities or strains or surface oxide layers, in order to incorporate them in magnetic circuits in later steps. For cutting, use is made of outer blade cutters, inner blade cutters, surface grinders, centerless grinders, lapping machines, etc.